Influence of Al and F Surface Modifications on the Sudden Death Effect of Si-Gr/Li1.2Ni0.2Mn0.6O2 Li-Ion Cells

Abstract : The dissolution, migration and deposition (DMD process) of transition metal ions during cycling is a well-known phenomenon reported in literature especially concerning high manganese spinel cathode 0246810121416182001020304050Pouch capacity ( mAh)Cycle index12SuddendeatheffectManganesedetectionat the anode sidePoint 1Point 2 2 material. The main approach to solve this issue consists in coating or doping the particles surface with electrochemically inert cations and/or anions. In this study, we describe a DMD process mechanism which happens in the silicon-graphite/lithium rich layered oxide (Si-Gr/Li1.2Ni0.2Mn0.6O2) systems. This phenomenon leads to a sudden death effect of the cell after 20 cycles. AlF3 coating is envisaged to limit the cation dissolution from the positive electrode: we highlight that our synthesis finally results in improving the electrochemical performances of lithium rich layered oxides by offering an Al/F doped surface. Despite this improvement, the coating fails, on the other hand, to stop the transition metal cations dissolution, especially in Li-ion cells (Si-Gr as anode).